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WO2024254575A2 - Réseau réflecteur térahertz amélioré et procédés associés - Google Patents

Réseau réflecteur térahertz amélioré et procédés associés Download PDF

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Publication number
WO2024254575A2
WO2024254575A2 PCT/US2024/033171 US2024033171W WO2024254575A2 WO 2024254575 A2 WO2024254575 A2 WO 2024254575A2 US 2024033171 W US2024033171 W US 2024033171W WO 2024254575 A2 WO2024254575 A2 WO 2024254575A2
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WO
WIPO (PCT)
Prior art keywords
reflectarray
signal
phase
transmit
processing unit
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
PCT/US2024/033171
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English (en)
Other versions
WO2024254575A3 (fr
Inventor
Nathan McKay MONROE
Refael WHYTE
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Cambridge Terahertz Inc
Original Assignee
Cambridge Terahertz Inc
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Cambridge Terahertz Inc filed Critical Cambridge Terahertz Inc
Publication of WO2024254575A2 publication Critical patent/WO2024254575A2/fr
Publication of WO2024254575A3 publication Critical patent/WO2024254575A3/fr
Anticipated expiration legal-status Critical
Pending legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
    • H04B10/90—Non-optical transmission systems, e.g. transmission systems employing non-photonic corpuscular radiation
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B2210/00—Indexing scheme relating to optical transmission systems
    • H04B2210/006—Devices for generating or processing an RF signal by optical means

Definitions

  • inventions of this disclosure comprise improvements to high angular resolution beam steering terahertz antenna arrays, and in particular, refl ectarrays.
  • the device comprises a transceiver and reflectarray.
  • a transmit (TX) signal is split into transmit and receive pathways, and in each case to the input of a driver.
  • the output of the driver in the transmit pathway is connected to a duplexer (represented as a Wilkinson power combiner in this case) and thereby to a feed point of the reflectarray, which comprises a plurality of antenna elements.
  • the incident wave is reflected by the reflectarray in a direction of interest, where it may encounter one or more objects and be reflected back toward the reflectarray. Waves reflected back toward the reflectarray are directed to the duplexer and thereby to the receive pathway and associated processing.
  • Each antenna element of the reflectarray may comprise a phase shift circuit.
  • the phase shift circuit may be a one-bit phase shifter as depicted in Figure
  • the signal D controls two switches comprising for example, complementary metal-oxide semiconductor (CMOS) field effect transistors.
  • CMOS complementary metal-oxide semiconductor
  • a logic high on signal D activates the switch that connects Pl to P2
  • a logic low on signal D activates the switch that connects Pl to P3.
  • the one-bit phase shifter embodiment of Figure 2 changes the phase with which an incident wave is reflected.
  • the reflected wave has a relative phase shift of 180 degrees depending on whether D is logic high or logic low.
  • Antenna elements may also comprise memory to store certain phase shift values to be applied at certain times.
  • Those of ordinary skill in the art will understand that the reflectarray device illustrated in Figures 1-2 are only one embodiment in which the inventions of this disclosure may be implemented and do not limit the following teachings. The teachings of this disclosure are applicable to other means of phase shifting and reflectarrays implemented with different or additional technologies.
  • the inventions of this disclosure comprise a method of modulating the phase pattern applied to a reflectarray imaging radar during sampling of a single pixel.
  • the reflectarray may act as a mixer and produce an output at a reduced intermediate frequency (IF).
  • the inventions of this disclosure comprise Terahertz (THz) reflectarray patch antennas fabricated in flip chip (or controlled collapse chip connection) packages and the inclusion of passive resonators in or on the board to which such packages are attached.
  • THz Terahertz
  • the inventions of this disclosure include locating a processing unit near or within an antenna element of the reflectarray.
  • a processing unit co-located with a patch antenna computations performed to calculate each antennas’ phase state may be made in realtime on-chip, rather than being pre-computed and loaded onto an on-chip memory.
  • Figure 1 depicts an illustrative reflectarray radar design in which aspects of the instant disclosure may be implemented.
  • Figure 2 exemplary design of a one-bit phase shifter associated with a single patch antenna of the reflectarray.
  • Figure 3a shows a sample radar output without range gating.
  • Figure 3b shows a sample radar output with range gating via local oscillator in the output path.
  • Figure 4 shows a mixer placed in the radar output signal path for range gating, where the exemplary radar output signal path includes a 625 megahertz (MHz) local oscillator, mixer, variable gain amplifier, analog-to-digital converter (ADC) operating at 15 mega-samples per second (MSPS), and a computer for processing.
  • MHz gigahertz
  • ADC analog-to-digital converter
  • Figure 5 shows a one-bit reflectarray phase pattern for a certain instance of beam steering (left), and its inverted state (right). Black squares represent antennas with a phase state of 0°, and white squares represent antennas with a phase state of 180°, resulting in exact inversion of the two patterns.
  • Figure 6 depicts an exemplary radiation pattern magnitude of the reflectarray, applicable in both cases of phase patterns from Figure 5.
  • Figure 7 depicts exemplary radiation pattern phases of the reflectarray associated with the two configurations in Figure 5, showing that, in all directions, the two sets of phases have a 180-degree difference between them.
  • Figure 8 depicts the phase modulation term applied to the radar output IF signal resulting from reflectarray pattern inversions.
  • Figure 9 depicts a typical CMOS cross section.
  • Figure 10 depicts simulation data showing typical radiation efficiencies for a 300 gigahertz (GHz) patch antenna in a CMOS process, as a function of the separation distance between the patch antenna’s radiating element and ground.
  • GHz gigahertz
  • Figure I la depicts wirebond connections for chip-chip and chip-board interconnect.
  • Figure 1 lb depicts a flip-chip assembly.
  • Figure 11c depicts a flip-chip assembly with passive radiators.
  • Figure 12 depicts an antenna array chip with input-output (I/O) pads arranged around the periphery.
  • Figure 13 depicts an array of chips.
  • Figure 14 depicts a metallized printed circuit board (PCB) to host the array of chips.
  • PCB printed circuit board
  • Figure 15 depicts a side view of flip chip antenna array on superstrate PCB.
  • the inventions of this disclosure comprise, in one aspect, a method of modulating the phase pattern applied to a reflectarray imaging radar during sampling of a single pixel.
  • the reflectarray may act as a mixer and produce an output at a reduced intermediate frequency (IF).
  • a single transceiver is used to generate an image one pixel (or few pixels) at a time in a single-in, single-out (SISO) fashion. See Figure 1.
  • a single transceiver is preferred due to constraints in building dense transceiver arrays.
  • a typical useful image resolution of such a reflectarray radar might be, for example, 200x400 pixels. At ten frames per second, a reflectarray radar with this resolution would sample nearly one million pixels per second. Because each pixel is sampled serially, the maximum allowable integration time per pixel in such a design is on the order of 1 microsecond.
  • range resolution requirements are often finer than 5mm, which translates to a chirp bandwidth of 30GHz.
  • the requirement to chirp over a wide bandwidth in a short time yields very high chirp ramp rates in excess of 30GHz/ps and therefore very high frequencies at the radar’s output, often in the hundreds of MHz or GHz for targets within tens of meters. See Figure 3a.
  • High output frequencies place constraints on downstream analog to digital converters (ADCs) and signal processing paths, adding cost, complexity and power consumption while also reducing noise performance.
  • ADCs analog to digital converters
  • a mixer placed in the radar output signal path can perform a “range gating” function by mixing the radar’s output signal down to a lower frequency, as seen in Figure 4. Mixing the output signal in this way relaxes the constraints on the ADC and downstream signal processing. However, it comes at the expense of reducing the widow of possible ranges which are visible to the radar, as seen in Figure 3b.
  • the addition of the range gating mixer (and associated local oscillator) add cost, power, complexity, phase noise, and other nonidealities.
  • common target scenes have abrupt changes in target distance, requiring rapid changes in range gating configuration and therefore rapid changes in the range gating mixer’s Local Oscillator frequency.
  • this mixing function can alternatively be performed by the reflectarray itself by modulating the phase pattern of the array.
  • the phases of the antenna in the reflectarray alter the radar’s intermediate frequency (IF) output by changing the direction to which the radar is sensitive.
  • the refl ectarray’s phases can also be used to apply modulation to the radar’s IF output while preserving the direction of the radar’s sensitivity.
  • the array’s phases are repeatedly altered between a first state and the inversion of the said first state, as illustrated by Figure 5.
  • the direction and magnitude associated with the current pixel to be sampled are preserved between the first state and its inversion (see Figure 6), while the two states have radiation pattern phases which are 180 degrees relative to one another (see Figure 7). Therefore, by rapidly switching between the two states, a square wave modulation is applied in the phase of the radar’s output signal, as seen in Figure 8.
  • Appropriate values of the modulation frequency can allow the reflectarray to serve as the range gating mixer. This approach reduces part count, cost, complexity, power, and phase noise. It also eliminates settling time issues, enabling the radar imager to have agility in accepting a wide range of distances simultaneously.
  • phase-shift pattern applied to the reflectarray between a first state associated with the current pixel to be sampled and the inverse of the first state at a frequency of 25MHz results in an IF of 25MHz and a range of useful sensing distances of 1-1.5 meters for an ADC with a sampling rate of 50MSPS.
  • the inventions of this disclosure may also comprise Terahertz (THz) reflectarray patch antennas fabricated in flip chip (or controlled collapse chip connection) packages and the inclusion of passive resonators in or on the board to which such packages are attached.
  • THz Terahertz
  • the radiation efficiency is closely related to the distance between the radiating element and the lower ground plane, with a larger distance corresponding to a higher efficiency, as seen in simulation data in Figure 10.
  • this distance is limited by manufacturing constraints, leading to typical efficiencies around 25% (-6dB).
  • this radiation efficiency penalty is seen four times, with a total loss of 24dB, or more than 99.6%.
  • SNR Signal-to- Noise Ratio
  • Increased integration time directly manifests in reduced imaging framerates by the same factor.
  • on-chip antennas suffer limited bandwidth, often approximately 3%, or 10GHz at a center frequency of 300GHz. Limited bandwidth directly manifests in reduced range resolution, with many applications requiring 5mm of range resolution, translating to 30GHz of bandwidth.
  • flip-chip assembly is utilized to address the two issues described above.
  • Flip-chip packaging and processes enables rapid assembly with connections made in parallel, as seen in Figure 1 lb.
  • flip chip packaging and assembly addresses the antenna efficiency and bandwidth issues summarized above.
  • Passively radiating metal structures can be located on the same side of the substrate material as the chips, the opposite side, integrated within the superstrate material, or any combination of the above.
  • the IC with on-chip antennas has input/output (VO) pads arranged around its periphery, as seen in Figure 12, and a plurality of such chips are arranged in an array, as seen in Figure 13.
  • VO input/output
  • Figure 14 depicts the superstrate printed circuit board (PCB) which hosts the array of chips, depicting the metallization which is used for both interconnect between chips (the lines) and the passively radiating structures (the squares).
  • PCB printed circuit board
  • the superstate PCB material could be a standard RF PCB material such as those made by Rogers Corporation, or alternatively, alumina, glass or quartz materials in some incarnations.
  • a plurality of metallic shapes on the PCB, which serve as passive radiators, can assume multiple shapes. In some shapes, slots or cuts are made into the passively radiating metal structure to improve efficiency, bandwidth or coupling performance.
  • CMOS-based large antenna arrays realtime imaging requires rapid switching of beam states, which necessitates impractically large digital bandwidths to control phase states for the antenna array. Such requirements are often in excess of 10 Gbps for realtime imaging with reasonable frame rates, a data rate that introduces severe challenges on system power and performance.
  • the computation ability that comes with CMOS processing can address this.
  • CMOS THz antenna arrays with certain configurations leave significant amounts of silicon and routing resources available for use to be applied to this control bandwidth problem.
  • Existing reflectarray designs utilized these resources for on- chip memory, such that each antenna locally stores a library of pre-computed beam states which are loaded onto the array’s on-chip memory at startup.
  • a device and method herein described addresses this bandwidth challenge and the memory silicon area limitations by locating a processing unit near or within an antenna element of the reflectarray. With a processing unit co-located with a patch antenna, computations performed to calculate each antennas’ phase state may be made in realtime on- chip, rather than being pre-computed and loaded onto an on-chip memory.
  • computation circuits replace the local on-chip memory so that each antenna locally computes the required phases for beam steering, rather than using on- chip memory to store externally pre-computed beam states.
  • Each antenna locally contains computation circuits executing a local model of the reflectarray system capable of calculating its own required phase in realtime.
  • each antenna is loaded with a small number of bits (perhaps on the order of 200) to communicate its physical location within the reflectarray and the system geometrical parameters. Subsequently, in operation mode, the desired beam direction (a ⁇ 16 bit number) is communicated to each antenna simultaneously.
  • On-chip computation circuits within each antenna may use this information to calculate the antenna’s specific phase state, with each antenna operating simultaneously in parallel. Performing calculations at each antenna element reduces the startup bandwidth requirement to a negligible amount and operation-time bandwidth to an acceptable amount ( ⁇ 16MHz), and reduces the chip area requirement to negligible amounts which are compatible with future cost-reduced versions employing off-chip antennas.
  • reflectarrays are implemented by designing a CMOS chip such that it can communicate with copies of itself, and tiling many copies of such chips into a large array.
  • the related dicing and assembly process adds unnecessary steps due to the labor, equipment, required tolerances and yield issues.
  • a full reticle is filled with antenna array circuits, and a wafer is fabricated filled with such reticles.
  • a low cost and low fidelity post-processing step performed on the wafer stitches adjacent reticles, yielding an antenna array with much simpler and cheaper assembly.
  • the improvements of the instant disclosure may enable not only cost- and power-savings but also miniaturization to a point where a reflectarray with an integrated transceiver in a monostatic radar configuration may be manufactured in a handheld form factor for portable THz imaging.

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  • Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Electromagnetism (AREA)
  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Variable-Direction Aerials And Aerial Arrays (AREA)

Abstract

L'invention concerne des améliorations apportées à des systèmes d'imagerie térahertz et leurs procédés d'utilisation associés. Dans des systèmes d'imagerie térahertz comprenant un réseau d'antennes térahertz constitué d'une pluralité d'éléments d'antenne ayant chacun une antenne à plaque et un déphaseur à un bit, le motif de phase appliqué par chaque déphaseur peut commuter de telle sorte que le réseau réflecteur lui-même peut agir en tant que mélangeur dans le trajet de signal. De tels réseaux réflecteurs peuvent être avantageusement mis en œuvre avec des boîtiers à puce retournée comportant des résonateurs passifs, et une unité de traitement peut coopérer avec chaque antenne à plaque pour calculer le signal d'attaque approprié au déphaseur.
PCT/US2024/033171 2023-06-09 2024-06-08 Réseau réflecteur térahertz amélioré et procédés associés Pending WO2024254575A2 (fr)

Applications Claiming Priority (6)

Application Number Priority Date Filing Date Title
US202363507236P 2023-06-09 2023-06-09
US202363507229P 2023-06-09 2023-06-09
US202363507219P 2023-06-09 2023-06-09
US63/507,219 2023-06-09
US63/507,236 2023-06-09
US63/507,229 2023-06-09

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WO2024254575A2 true WO2024254575A2 (fr) 2024-12-12
WO2024254575A3 WO2024254575A3 (fr) 2025-01-30

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US8022861B2 (en) * 2008-04-04 2011-09-20 Toyota Motor Engineering & Manufacturing North America, Inc. Dual-band antenna array and RF front-end for mm-wave imager and radar
US9461367B2 (en) * 2013-01-23 2016-10-04 Overhorizon Llc Creating low cost multi-band and multi-feed passive array feed antennas and low-noise block feeds
CN118117305A (zh) * 2016-12-21 2024-05-31 英特尔公司 无线通信技术、装置和方法
US11474233B2 (en) * 2017-12-21 2022-10-18 Georgia Tech Research Corporation System for sensing backscatter tag communications from retrodirective antenna arrays
US11870152B2 (en) * 2021-08-19 2024-01-09 Advanced Semiconductor Engineering, Inc. Electronic device

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